Spin-driven electrical power generation at room temperature

Abstract

Ongoing research is exploring novel energy concepts ranging from classical to quantum thermodynamics. Ferromagnets carry substantial built-in energy due to ordered electron spins. Here, we propose to generate electrical power at room temperature by utilizing this magnetic energy to harvest thermal fluctuations on paramagnetic centers using spintronics. Our spin engine rectifies current fluctuations across the paramagnetic centers' spin states by utilizing so-called 'spinterfaces' with high spin polarization. Analytical and ab-initio theories suggest that experimental data at room temperature from a single MgO magnetic tunnel junction (MTJ) be linked to this spin engine. Device downscaling, other spintronic solutions to select a transport spin channel, and dual oxide/organic materials tracks to introduce paramagnetic centers into the tunnel barrier, widen opportunities for routine device reproduction. At present MgO MTJ densities in next-generation memories, this spin engine could lead to 'always-on' areal power densities that are highly competitive relative to other energy harvesting strategies.

Encoding Information on the Excited State of a Molecular Spin Chain

“…These results constitute direct evidence in magnetotransport of spintronic anisotropy, [ 28,52 ] that is, a change in magnetic anisotropy caused by a spin‐polarized current, [ 28,52 ] here due to spin excitations along MSCs. As another manifestation, while the R ( H ) loop for V = 65 mV (Figure 2c) resembles that of V = 80 mV (Figure 2a), maximizing the spin‐flip conductance at 73 meV (i.e., at the d I/ d V peak) results in a strongly distorted R ( H ) (Figure 2b).…”

“…We also use a phenomenological macrospin model of transport to pinpoint the role of magnetic coupling between the spin chain and the FM electrode in promoting this encoding capability. Our work thus implements the exchange bias concept [ 31 ] at ferromagnetic metal/molecule interfaces [ 15,41,42 ] (so‐called “spinterfaces” [ 33 ] ) within the device's active spintronic layer, and articulates it with the concepts of spin‐flip spectroscopy [ 14 ] and spintronic anisotropy, [ 28,52 ] thanks to magnetotransport across solid‐state molecular vertical nanojunction devices. Our work thus extends prior magnetotransport research across antiferromagnetic materials [ 21–25 ] into the quantum regime, and hints at interesting magnetometry studies [ 53 ] of the spin chain's ground and excited states.…”

“…This can also help increase the spintronic harvesting of thermal energy fluctuation on paramagnetic centers. [ 28 ]…”

“…[ 26,27 ] More generally, building spintronic devices that address discrete spins not only advances well‐established strategies to encode/transmit quantum information, [ 3,7–13 ] but also emerging strategies to harvest thermal energy. [ 28 ] Using paramagnetic molecules, [ 29 ] rather than atoms in an inorganic matrix, [ 28 ] advantageously enables the straightforward integration of these spin states into device stacks. In this paper, we overcome the resulting technological challenge of processing these solvent‐sensitive, fully in situ grown stacks into vertical nanodevices.…”

Record thermopower found in an IrMn-based spintronic stack

“…Spin caloritronics [4][5][6][7][8] is an interdisciplinary field which merges spintronics [9][10][11] with thermoelectrics [12][13][14][15][16][17][18][19] and has attracted tremendous attentions lately. A key device within spintronics and the IoT, and thus an attractive target to consider for spin caloritronics, is the magnetic tunnel junction (MTJ) [20][21][22][23] . The MTJ typically consists two ferromagnetic (FM) layers, separated by a thin insulating layer, with one of the magnetic layers pinned by exchange bias to an antiferromagnet, with IrMn being a popular choice.…”